Manufacture of chlorinated compounds



United States ?atent 6 MANUFACTURE OF CHLORINATED CGMPOUNDS Morton Kleiman, Chicago, 111., assignor to Velsicol Chemical Corporation, a corporation of lilinois No Drawing. Application June 13, 1950, Serial No. 167,921

2 Claims. (Cl. 260-648) This invention relates to the chlorination of 4,5,6,7,8,8- hexachloro 3a,4,7,7a tetrahydro 4,7 methanoindene, hereinafter termed chlordene, and to the material resulting therefrom. More specifically, this invention relates to a novel means of chlorinating chlordene with chIorine in the presence of polyvalent metal silicate catalyst with the attendant advantages hereinafter described.

It is one object of the present invention to provide a new and improved method for preparing l,4,5,6,7,8,8- heptachloro 3a,4,7,7a tetrahydro 4,7 methanoindene by directly chlorinating chlordene with chlorine specifically in the presence of said catalyst.

Another object of the present invention is to provide a means for chlorinating chlordene with chlorine so as to directionalize the reaction and greatly increase the amount of the more insecticidally toxic material, l,4,5,6,7,8,8- heptachloro 3a,4,7,7a tetrahydro 4,7 methanoindene in the chlorinated reaction product mixture over that which may be formed when chlordene is chlorinated by means heretofore used.

Another object of this invention is to increase chlorination by substitution and diminish chlorination by addi tion when reacting chlordene with chlorine.

Another object of this invention is to provide a very rapid or accelerated method for chlorinating chlordene with chlorine without necessitating the use of elevated temperatures and without danger of discoloration or decomposition by the use thereof.

Another object is to provide a rapid means for chlorinating chlordene without using excess chlorine.

These and other objects and advantages of the present invention will be apparent from the following specification.

Broadly, the present invention relates to a novel and improved method for chlorinating chlordene, namely, chlorinating chlordene with chlorine in the presence of a polyvalent metal silicate or mineral silicate as a catalyst.

Chlordene, the starting material in the process herein disclosed, is that material resulting from the Diels-Alder adduction of hexachlorocyclopentadiene and cyclopentadiene in accordance with the folowing equation:

01 H 01 oi 01 ll 01- o1 oi or U 01 HH 1 H HH Hexachlorocyclo- Cyclopenta- (Chlorden pentadiane diene 4,5,6,7,8.8-hexachloro-3a4,7,7a-

tetrahydro-4,7-methanolndene 'ice Chlordene can be prepared simply by intermixing hexachlorocyclopentadiene and cyclopentadiene, preferably in the absence of additional solvent. The reaction proceeds in a satisfactory manner at room temperature and also may be accomplished at cooler or more elevated temperatures. The reaction is somewhat exothermic and the temperatures thereof should be controlled such that temperatures not exceeding about 200 C. and preferably not exceeding IOU- C. are maintained throughout the course of the reaction. The reactants may be utilized in a molar ratio of 1:1; however, an excess of either reactant can be present. The reaction product, namely the adduct of hexachlorocyclopentadiene and cyclopentadiene is crystalline in nature and may be purified by recrystallization from a solvent such as methanol.

Thus, as a specific method for preparing the aforementioned adduct, hexachlorocyclopentadiene may be placed in a vessel equipped with a mechanical stirrer, thermometer and reflux condenser. The hexachlorocyclopentadiene may then be heated to about 70 C. and have added thereto in a portionwise manner an equal molar quantity of cyclopentadiene. The reaction temperature may be maintained at about 70-85 C. After the cyclopentadiene has been completely added, the stirring may be continued for several hours. The crystalline material thus formed may be purified by recrystallization one or more times from methanol.

While a general and specific method for preparing chlordene has been above presented, it is expressly stated that the present invention is not dependent on those or any particular source or origin of chlordene; and the present process can be applied to the material having the chemical structure represented for chlordene regardless of its derivation or method of manufacture and the chlordene may be employed in either substantially pure form or in the form of a crude reaction mixture resulting from the aforesaid or other process for manufacture thereof.

Chlordene, being unsaturated and not completely substituted, can be chlorinated with chlorine in the liquid phase in the absence of a catalyst; however, while such a process is satisfactorily operable, the present process possesses many advantages which are not present in the prior art process.

Although chlordene has two olefinic linkages, namely between carbon atoms 2 and 3 and between carbon atoms 5 and 6 respectively, only the olefinic linkage between carbon atoms 2 and 3 can be saturated with chlorine under ordinary or even under rigorous conditions. The hydrogen substituents of carbon atoms 5 and 6 are completely substituted by halogens thereby rendering the olefinic linkage between said carbon atoms peculiarly inert under the chlorination conditions herein contemplated.

Having a reactive double bond, chlordene can be chlorinated by way of addition in accordance with the following reaction to form chlordane, a commercial insecticide.

Cl H H H 01 C -Cl 01- -C1 C1: I C1Cl G] H HE E HE H 01 \1 Chlordane Chlordane When chlorinating chlordene to form chlordane, in addition to obtaining saturation of the double bond, as shown above, a limited amount of chlorination by substitution occurs as a side reaction. The hydrogen atoms of carbon atom No. l is chlordene, which is allylic, are themselves somewhat activated, and it is the hydron n o n 01 -o-1 l o1---c1 l G1:-Cl 01 11 Cl 01 1,4,5,6,7,8,8-heptachloro-3a,4.7,7a- 1,2,3,4,5,6,7,8,8-nonachloro 3a;4.7, tetrahydro-4J-methanoindene -7a-tetrahydro4,7-methanomdane While other materials may be produced from the chlorination of chlordene with chlorine, they are relatively minor with respect to the amount of heptachlor or nonachlor usually produced, and are certainly negligible as compared to the amount of chlordane produced.

Of the three materials heretofore stated to be obtainable from the chlorination of chlordene with chlorine, by far the most potent one as an insecticide is heptachlor. It is therefore, greatly advantageous to be able to directionalize the chlorination of chlordene to form increased amounts of heptachlor. Alternatively stated, it is advantageous to directionalize the chlorination of chlordene with chlorine to greatly enhance chlorination by substitution with a substantial diminution of chlorination by addition as compared to that obtainable by prior methods.

The chlorination of chlordene with chlorine in the absence of a catalyst proceeds very slowly at lower temperatures such as those approaching normal room temperature or lower. Consequently, to maintain a practicable rate of reaction, somewhat elevated temperatures such as about 70 C. or even higher are generally and preferably used to complete the reaction in a reasonable period. The reaction time required to react a mole of chlorine per mole of chlordene in the absence of catalyst at about 70 C. may require as much time as 6 hours. The use of such elevated temperatures to increase the rate of reaction is disadvantageous for at least two reasons. Firstly, the chlordene and chlorinated products thereof may tend to discolor on being subjected to elevated temperatures for protracted periods, and secondly, the cost of maintaining reactants at elevated temperatures and maintaining temperature control must be considered.

The ordinary chlorination of chlordene with chlorine at temperatures such as room temperature is very slow and thus is not economical. For example, a reaction mixture of equimolar amounts of chlordene and chlorine dissolved in carbon tetrachloride is not completely reacted even after 24 hours. The reaction rate at room temperature may be somewhat increased by utilizing a large excess of chlorine such as by constantly bubbling chlorine .gas through the reaction mixture, but this is not advantageous in that either a large amount of chlorine gas is wasted or else a recovery system for the gas must be provided, operated and maintained. In addition, a large excess of chlorine promotes the formation of excessively chlorinated side products of decreased value.

.-A usual method generally employed for obtaining chlorination by substitution in preference to chlorination by addition is to carry out the chlorination at very high temperatures, usually in the vapor phase. This usual method cannot be applied to chlordene, however, because the temperatures required for a vapor phase chlorina- 4 tion would cause the reactant and products to decompose. The present invention contemplates a method completely different from the usual method above stated for effecting substitution chlorination rather than addition chlorination in chlordene.

As hereinbefore stated, the present invention relates to the improvement in the process for chlorinating chlordene with chlorine which comprises efiecting said process in the presence of polyvalent metal silicate, or alternatively termed, mineral silicate as a catalyst. Since chlordene decomposes before it volatilizes under ordinary pressures, the catalytic chlorination herein contemplated is effected in the liquid phase with the chlordene preferably dissolved in a suitable solvent. The use of any particular solvent is not critical, it being desirable, however, that the solvent used be substantially unreactive with chlorine under the reaction conditions used. Exemplary of solvents which may be used with excellent results are carbon tetrachloride, chloroform, tetrachloroethane, hexachloroethane, nitrobenzene, Freon, or like halogenated organic or otherwise relatively inert solvents. Other solvents which can be used with substantially equal facility will naturally be suggested to those skilled in the halogenation art.

The amount of solvent used is not critical. It is pre ferred that there be a sufficient amount used to completely dissolve the chlordene. An excess of solvent, i. c. more than is suflicient to dissolve the reactants may be used without harmful results; however, a very large excess should be avoided so as to minimize the size of the reaction vessel and so as to avoid excessive diminution of the rate of reaction because of excessive dilution of the reactants.

The catalyst used has been defined as polyvalent metal silicate or mineral silicate. Exemplary of this type of catalyst is the montmorillonite group of minerals such as montmorillonite, beidellite, nontranite, hectorite, saponite; the hydrated mica group of minerals such as talc, biotite, muscovite; the kaolin group of minerals such as cherokee clay, sheridan clay, kaolinite; the polygorskite group of minerals such as attapulgite; aluminum silicates such as zeolites, both natural and synthetic. Generally, those complex silicates of polyvalent metals which occur naturally or which can be prepared synthetically are applicable to the present process.

It is preferred that the catalyst be activated, i. e. granular, porous, adsorptive and possessing a relatively high ratio of surface to mass. it is also preferred that these catalysts be further activated by heating to drive off uncombined volatile material such as water.

Activation of these catalysts may be efiected by treating them with a mineral acid such as sulfuric acid and/or by particleexpansion according to known means. Further activation by controlled dehydration can be accomplished by heating as above indicated or by heating at lower temperatures in vacuo, or by contacting with .dehydrating agents such as calcium chloride. Excessive heating such as will fuse the porous catalyst should be avoided.

The following table gives detailed analyses of several polyvalent metal silicates which have been found useful.

Table Diatomaceous earth (Celattfrn- Eag Picher Co.)

Kaolin (Cherokee 'C. Vanderbilt Co.)

Percent Ignition Loss Fullers Fuller's Fuller's Earth Earth Earth (Flore: (Floridin (#9022- XX- XX- General Floridln Floridin Reduc- Oo.) 00.) tion pH 7. 9-8. 2 7. 9-8. 2 Percent 810:. 57. 52 57. 52 69. 62 Percent A110: 15. 43 15. 43 14. 34 Percent Mae. 2. 44 2. 44 1. 0 Percent Pesos" 4. 95 4. 95 3. 9 Percent 080 1. 75 1. 75 0. 8 Percent Tl0- 0. 7 Percent H2O 6.4 6. 4 Percent Ignition Loss 9. 4 9. 4 6. 7

i ii s um-. u- Kaonn mlnum Silicate i l Silicate (Flltrol win its is? Fair;

0 GlayMlnes) derbnt 5.4 Percent $102. 59.0 61. 1 63. 18 Percent A120: 27. 81 9. 03 15.07 Percent MgO 0.29 13. 7 4. 40 Percent F8203" 0.78 0. 9 2. 20 Percent 0:10..-. 0.21 2. 7 0.30 Percent T101... 1. 21 0. 1 0. 57 Percent H2O 1-2 6. 40 Percent Ignition Loss 10.6 18. 30 Percent No.20--. 13.15

Synthetic aluminum silicates were prepared and found useful as hereinafter shown. Similarly polyvalent metal silicates, Houdry M-46, Filtrol X-417 and Filtrol X-202 are useful.

It is desirable that the catalyst surface be intimately contacted with the reaction mixture. Therefore, a relatively small particle size, presenting a large surface in proportion to mass is preferred. While the preferred particle size may vary depending on the amount of catalyst used and the size and type of reactor utilized, under usual conditions a catalyst having a particle size of less than about 50 mesh is preferred.

In the present process the polyvalent metal silicate catalyst acts as a true catalyst. That is, the process is effected by and operable with amounts of catalyst which are ordinarily termed catalytic amounts. Thus, an amount of catalyst, representing only about 0.5% by weight of the chlordene chlorinated gave very satisfactory results both as to increasing the yield of heptachlor and increasing the rate of reaction. Conversely, much larger amounts of catalyst can be used, such as, for example, an amount equivalent to about 25% by weight of the chlordene chlorinated. There does not appear to be a maximum limit as to the quantity of catalyst which can be used; however, to avoid obtaining a thick slurry which is difiicult to manage, and in the interests of economy, it is recommended that for convenience catalyst in the amount of less than about 10% by weight of the chlordene reactant be used.

Since the principal product desired is heptachlor, it is preferred that about a stoichiometric amount of chlorine with respect to chlordene be used to produce said principal product. Thus, the optimum ratio of reactants, namely of chlorine to chlordene, is about 1 to 1 or about equimolar. While less than an equimolar amount of chlorine based on chlordene may be used, it is uneconomical to do so since this will result in incomplete reaction of the chlordene, thereby contaminating the product with reactant. The use of large excesses of chlorine is undesirable in that it is wasteful of chlorine and further may lead to the production of undesirable side products. It will be noted that the amount of chlorine introduced into the reaction chamber is not critical provided the reaction is terminated when about 0.75 to about 1.25 mole equivalents of chlorine have reacted chlorine and catalyst may be added together in any orderv or sequence. One method, is to dissolve the chlordene in solvent, add the catalyst and then add the chlorine. Variations of this procedure are, however, satisfactory.

As heretofore stated, the catalytic reaction of the present invention proceeds quite rapidly. Ordinarily, not more than an hour is required for the reaction to proceed to completion, and generally, even a lesser time than this is suflicient. By the reaction having proceeded to completion is meant that point at which about a mole of chlorine has reacted with a mole of chlordene, or if less than a mole of chlorine per mole of chlordene is present, the point where substantially all the chlorine has reacted. Excessive reaction periods are not harmful, especially where equimolar or .less quantities of chlorine based on chlordene are used. Chlordene in the presence of 50% excess chlorine was allowed to react for an extended period, namely 3 hours, in the presence of fullers earth and still a preponderant yield of heptachlor was obtained. At high temperatures, it is undesirable to unduly prolong the reaction time where large excesses of chlorine are present because of the possibility of reactions between heptachlor originally formed and the excess chlorine to form other, less desirable products.

It is a simple matter to trace the reaction and determine the extent of its completion by titrating aliquot portions of the reaction mixture as the reaction progresses to determine the amount of unreacted chlorine contained therein.

The maximum temperature limitation appears to be that which normally limits every chemical reaction, namely, that temperature at which the reactants or prod ucts decompose. In the present case, this is about 160 C. The reaction also proceeds at very low temperatures with effective results being obtained at temperatures as low as for example -35 C. depending on the freezing point of the solvent used.

A favorable temperature range within which the reaction proceeds rapidly without darkening or other harmful eifects is about 20 C. to about C. A preferred range which is most economical to use from a standpoint of fuel consumption, quality of product, and rate of reaction is about 15 C. to about 45 C.

Exemplary of the general method employed in the present process, chlordene is dissolved in a solvent and a catalyst as previously defined is added thereto. Maintaining this mixture at the desired temperature, chlorine gas is introduced into the mixture with stirring. A molar equivalent of chlorine, based on chlordene, can generally be introduced at a relatively rapid rate without any loss of chlorine and without resorting to pressure vessels. Any technique known to the art for reacting a measured amount of chlorine with a liquid reactant under the present conditions is satisfactory. The course of the reaction can be traced by titrating aliquots of the mixture as hereinbefore stated. When the reaction is completed, catalyst can be removed by decantation, filtration or like means; hydrogen chloride, any excess chlorine, and solvent may be removed from the product by any means known to the art such as alkaline wash followed by distillation, at reduced pressure if desired. Where both excess chlorine and solvent are removed by distillation, it is preferred that the removal be accomplished at reduced pressure to avoid prolonged reaction periods at elevated temperatures. Alternatively, the chlorine can be removed by stripping with an inert gas such as nitrogen. The product which is rich in its heptachlor component can be used as such without further treatment. Alternatively, the heptachlor can be purified by recrystallization from a suitable solvent or by chromatographic means. Suitable solvents for purifying the heptachlor product are methanol, butanol, pentane,

applied as measured droplets to the head capsules of male and female German roaches. The dosage levels were calculated in terms of micrograms of toxicant per insect. Following is a table of the results obtained.

Percent Mortality, Percent Mortality, Compound and Males Females DosagePin fiat?!"- grams er as N o. No.

Used 24 Hrs. 48 Hrs. Used 24 Hrs. 48 Hrs.

Heptachlor:

2O 25 75 50 46 98 50 15 4O 83 100 40 74 20 100 100 30 B3 20 0 0 30 l0 I7 40 3 3 40 10 4D 30 30 33 2O 20 70 30 40 40 In the above table, the per cent mortality for both the male and female roaches was noted after a 24 and 48 hour period. It is known, and corroborated by these results that female roaches are more difi'icult to kill than are male roaches, and for that reason the tests are run on each sex individually. The results indicate that heptachlor is four times as toxic as chlordane, and chlordane is far more toxic than nonachlor. To obtain about the same percentage kill on male roaches at 48 hours (namely about four times as much chlordane was required as was heptachlor (0.43 microgram of heptachlor to 1.72 micrograms of chlordane). Similarly to obtain the same percentage kill on female roaches at 48 hours (namely about 90%), four times as much chlordane was required as was heptachlor (1.72 micrograms of heptachlor to 6.88 micrograms chlordane).

The great superiority of heptachlor over chlordane and other chlorinated products of chlordene such as nonachlor from a toxicity standpoint is well known and corroborated by many investigators. Heptachlor is further superior to chlordane or the like because, while it is sufficiently chlorinated to provide a favorable residual toxicity, it vaporizes at a sufiicient rate to avoid leaving toxic residues on food products within a reasonable period after application thereof.

I claim as my invention:

1. A method for chlorinating 4,5,6,7,8,8-hexach1oro- 3(1,4,7,7a-tetrahydro-4,7-methanoindene which comprises reacting it with chlorine in a relatively inert solvent and in the presence of fullers earth as a catalyst at a temperature of from about 20 C. to about C. until from about 0.75 to about 1.25 mole equivalents of chlorine have reacted with each mole equivalent of said indene.

2. A method for chlorinating 4,5,6,7,8,8-hexachloro- 3a,4,7,7a-tetrahyclro-4,7-methanoindene which comprises reacting it with chlorine in a relatively inert solvent and in the presence of fullers earth as a catalyst at a temperature of from about 15 C. to about 45 C. until about one mole equivalent of chlorine has reacted with each mole equivalent of said indene.

References Cited in the file of this patent UNlTED STATES PATENTS 

1. A METHOD FOR CHLORINATING 4,5,6,7,,8,8-HEXACHLORO3A,4,7,7A-TETRAHYDRO-4,7-METHANOINDENE WHICH COMPRISES REACTING IT WITH CHLORINE IN A RELATIVELY INERT SOLVENT AND IN THE PRESENCE OF FULLER''S EARTH AS A CATALYST AT A TEMPERATURE OF FROM ABOUT -20* C. TO ABOUT 145* C. UNTIL FROM ABOUT 0.75 TO ABOUT 1.25 MOLE EQUIVALENTS OF CHORINE HAVE REACTED WITH EACH MOLE EQUIVALENT OF SAID INEDNE. 